Fluid flow control valves are known which use flexible diaphragms or diaphragm assemblies for sealing against a valve seat. The diaphragm is often "pressure balanced" so that inlet fluid pressure is seen on both the top and bottom sides of the diaphragm. The valve is opened by releasing fluid pressure from the top side of the diaphragm. This allows the fluid inlet pressure acting on the bottom side of the diaphragm to lift the diaphragm up off the valve seat, thereby opening the valve.
When the valve is to be closed, inlet fluid pressure has to be reintroduced into the pressure chamber located above the diaphragm. A small bleed hole can be placed in the diaphragm for allowing fluid to flow from one side of the diaphragm to the other, i.e. from the bottom to the top side of the diaphragm. Unfortunately, the water or other fluid passing through such valves is seldom "clean". Such water often contains suspended solids, such as grains of sand, which can clog the bleed hole and prevent the valve from functioning properly.
U.S. Pat. No. 3,254,664 to Delany et al shows a diaphragm valve having a bleed hole placed therein. The bleed hole is formed by a deformable hollow sleeve which is placed through a perforation in the diaphragm. At least one side of the sleeve is curled over in place to grip the diaphragm. This is done using a special mandril and punch. The sleeve itself forms the bleed hole.
A pin is then inserted through the bleed hole formed by the sleeve. The pin is retained in place by using a tool to flare the ends of the pin into a tapered fan-like shape. The pin is loosely slidable in the bleed hole and controls the rate of flow therethrough by virtue of its diameter. In addition, the pin can include impeller blades for rotating the pin to help keep the bleed hole clean.
The structure shown in the Delany patent for the bleed hole and pin is relatively cumbersome. For one thing, it requires the use of a separate element, i.e. the hollow sleeve, to form the bleed hole. In addition, various tools and manufacturing steps are required in assembling the components together. For example, at least part of the sleeve has to be curled over to retain it in the diaphragm. Moreover, a portion of the pin has to be flared to retain the pin inside the sleeve. These steps are all relatively difficult and time-consuming to do, especially when dealing with a relatively small bleed hole and pin as may be found in certain valves. This increases the difficulty and cost of manufacturing the valve.